黑河流域典型生态系统的降雨截留特征——基于高时间分辨率的土壤水分数据（英文）

Rainfall interception is of great significance to the fully utilization of rainfall in water limited areas.Until now,studies on rainfall partitioning process of typical ecosystems in Heihe River Basin,one of the most important inland river basins in China,is still insufficient.In this study,six typical ecosystems were selected,namely alpine meadow,coniferous forest,mountain steppe,desert,cultivated crop,and riparian forest,in Heihe River Basin for investigation of the rainfall interception characteristics and their influencing factors,including rainfall amount,duration,and intensity,based on the gross rainfall and high temporal resolution soil moisture data obtained from 12 automatic observation sites.The results show that the average interception amount and average interception rate of the six ecosystems are significantly different: alpine meadow 6.2 mm and 45.9%,coniferous forest 7.4 mm and 69.1%,mountain steppe 3.5 mm and 37.3%,desert 3.5 mm and 57.2%,cultivated crop 4.5 mm and 69.1%,and riparian forest 2.6 mm and 66.7%,respectively.The rainfall amount,duration,and intensity all had impact on the process of rainfall interception.Among these three factors,the impact of rainfall amount was most significant.The responses of these ecosystems to the rainfall characteristics were also different.Analyzing rainfall interception with high temporal resolution soil moisture data is proved to be a feasible method and need further development in the future.     

Analysis of water vapour flux between alpine wetlands underlying surface and atmosphere in the source region of the Yellow River

An underlying wetland surface comprises soil, water and vegetation and is sensitive to local climate change. Analysis of the degree of coupling between wetlands and the atmosphere and a quantitative assessment of how environmental factors influence latent heat flux have considerable scientific significance. Using data from observational tests of the Maduo Observatory of Climate and Environment of the Northwest Institute of Eco-Environment and Resource, CAS, from June 1 to August 31, 2014, this study analysed the time-varying characteristics and causes of the degree of coupling(Ω factor)between alpine wetlands underlying surface and the atmosphere and quantitatively calculated the influences of different environmental factors(solar radiation and vapour pressure deficit) on latent heat flux. The results were as follows:(1) Due to diurnal variations of solar radiation and wind speed, a trend developed where diurnal variations of the Ω factor were small in the morning and large in the evening. Due to the vegetation growing cycle, seasonal variations of the Ω factor present a reverse "U" trend. These trends are similar to the diurnal and seasonal variations of the absolute control exercised by solar radiation over latent heat flux. This conforms to the Omega Theory.(2) The values for average absolute atmospheric factor(surface factor or total) control exercised by solar radiation and water vapour pressure are 0.20(0.02 or 0.22) and 0.005(-0.07 or-0.06) W/(m2·Pa), respectively. Generally speaking, solar radiation and water vapour pressure deficit exert opposite forces on latent heat flux.(3) At the underlying alpine wetland surface, solar radiation primarily influences latent heat flux through its direct effects(atmospheric factor controls). Water vapour pressure deficit primarily influences latent heat flux through its indirect effects(surface factor controls) on changing the surface resistance.(4) The average Ω factor in the underlying alpine wetland surface is high during the vegetation growing season, with a value of 0.38, and the degree of coupling between alpine wetland surface and atmosphere system is low. The actual measurements agree with the Omega Theory. The latent heat flux is mainly influenced by solar radiation.     

How changes of groundwater level affect the desert riparian forest ecosystem in the Ejina Oasis,Northwest China

Groundwater is a key factor controlling the growth of vegetation in desert riparian systems. It is important to recognise how groundwater changes affect the riparian forest ecosystem. This information will not only help us to understand the ecological and hydrological process of the riparian forest but also provide support for ecological recovery of riparian forests and water-resources management of arid inland river basins. This study aims to estimate the suitability of the Water Vegetation Energy and Solute Modelling(WAVES) model to simulate the Ejina Desert riparian forest ecosystem changes,China, to assess effects of groundwater-depth change on the canopy leaf area index(LAI) and water budgets, and to ascertain the suitable groundwater depth for preserving the stability and structure of desert riparian forest. Results demonstrated that the WAVES model can simulate changes to ecological and hydrological processes. The annual mean water consumption of a Tamarix chinensis riparian forest was less than that of a Populus euphratica riparian forest, and the canopy LAI of the desert riparian forest should increase as groundwater depth decreases. Groundwater changes could significantly influence water budgets for T. chinensis and P. euphratica riparian forests and show the positive and negative effects on vegetation growth and water budgets of riparian forests. Maintaining the annual mean groundwater depth at around 1.7-2.7 m is critical for healthy riparian forest growth. This study highlights the importance of considering groundwater-change impacts on desert riparian vegetation and water-balance applications in ecological restoration and efficient water-resource management in the Heihe River Basin.     

Influence of short-term experimental warming on heat-water processes of the active layer in a swamp meadow ecosystem of the Qinghai-Tibet Plateau

Climate change is now evident in the Qinghai-Tibet Plateau(QTP), with impacts on the alpine ecosystem, particularly on water and heat balance between the active layer and the atmosphere. Thus, we document the basic characteristics of changes in the water and heat dynamics in response to experimental warming in a typical alpine swamp meadow ecosystem. Data sets under open top chambers(OTC) and the control manipulations were collected over a complete year. The results show that annual(2008) air temperatures of OTC-1 and OTC-2 were 6.7 °C and 3.5 °C warmer than the control. Rising temperature promotes plant growth and development. The freeze-thaw and isothermal days of OTCs appeared more frequently than the control, owing to comparably higher water and better vegetation conditions. OTCs soil moisture decreased with the decrease of soil depth; however, there was an obviously middle dry aquifer of the control, which is familiar in QTP. Moreover, experimental warming led to an increase in topsoil water content due to poorly drained swamp meadow ecosystem with higher organic matter content and thicker root horizons. The results of this study will have some contributions to alpine cold ecosystem water-heat process and water cycle under climate change.     

Simulation analysis on characteristics of land surface over western Qinghai-Xizang Plateau during freezing–thawing period

Using the Global Energy and Water Cycle Experiment—Asian Monsoon—Tibet Plateau Experiment (GAME-Tibet) observational data—from October 2002 through September 2003—of Gaize in the western Qinghai-Xizang Plateau (QXP), the land-surface characteristics of the Qinghai-Xizang Plateau are simulated by the improved land-surface model Common Land Model (CoLM). The results show that CoLM can reproduce the land-surface characteristics of plateau areas well. In the surface-energy balance of the western QXP in the winter half year, the sensible heat (SH) flux constituted the dominant energy, and the latent heat (LH, here and after) flux is very small. Although the LH flux nearly equals zero in freezing season, it cannot be ignored during the period of freezing–thawing in QXP. In the transition season from mid- to late-May, the frequent phase change of soil water that is caused by the freezing–thawing process leads to the increase of LH flux and decrease of the Bowen ratio. The simulation results also indicate that the changes of surface effective heat fluxes (SH and LH flux) are associated with precipitation and the frequent change between freezing and thawing processes in soil surface.     

城市地表热通量遥感反演及与土地类型的关系(英文)

Using ASTER(Advanced Spaceborne Thermal Emission and Reflection Radiome-ter) infrared remote sensing data we inversed the parameters of urban surface heat fluxes applying the PCACA model and theoretical position algorithm,and then we analyzed the in-fluence of different land use types on the surface heat fluxes and energy balance.In this study,Kumagaya,a city in Saitama Prefecture,Japan,was selected as the experimental area.The result shows that the PCACA model is feasible for the surface heat fluxes estimation in urban areas because this model requires less parameters in the procedure of heat fluxes estimation in urban areas with complicated surface structure and can decrease the uncertainty.And we found that different land-use types have indicated the height heterogeneity on the surface heat fluxes significantly.The magnitudes of Bowen ratio in descending order are industrial,residential,transportation,institutional,dry farmland,green space,and water body.Under the same meteorological condition,there are distinct characteristics and regional differences in Bowen ratios among different surface covers,indicating higher sensible heat flux and lower latent heat flux in the urban construction land,while lower sensible heat flux and higher latent heat flux in the vegetation-covered area,the outskirt of the urban area.The increase of urban impervious surface area caused by the urban sprawl can enlarge the sensible heat flux and the Bowen ratio,so that it causes the increasing of urban surface temperature and air tem-perature,which is the mechanism of the so-called heat island effect.     

Simulated effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region of the Northern Hemisphere

Soil freeze-thaw process is closely related to surface energy budget,hydrological activity,and terrestrial ecosystems.In this study,two numerical experiments(including and excluding soil freeze-thaw process)were designed to examine the effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region in the Northern Hemisphere based on the state-of-the-art Community Earth System Model version 1.0.5.Results show that in response to soil freeze-thaw process,the area averaged soil temperature in the shallow layer(0.0175?0.0451 m)decreases by 0.35℃in the TP(Tibetan Plateau),0.69℃in CES(Central and Eastern Siberia),and 0.6℃in NA(North America)during summer,and increases by 1.93℃in the TP,2.28℃in CES and 1.61℃in NA during winter,respectively.Meanwhile,in response to soil freeze-thaw process,the area averaged soil liquid water content increases in summer and decrease in winter.For surface heat flux components,the ground heat flux is most significantly affected by the freeze-thaw process in both summer and winter,followed by sensible heat flux and latent heat flux in summer.In the TP area,the ground heat flux increases by 2.82 W/m2(28.5%)in summer and decreases by 3.63 W/m2(40%)in winter.Meanwhile,in CES,the ground heat flux increases by 1.89 W/m2(11.3%)in summer and decreases by 1.41 W/m2(18.6%)in winter.The heat fluxes in the Tibetan Plateau are more susceptible to the freeze-thaw process compared with the high-latitude frozen soil regions.Soil freeze-thaw process can induce significant warming in the Tibetan Plateau in winter.Also,this process induces significant cooling in high-latitude regions in summer.The frozen ground can prevent soil liquid water from infiltrating to deep soil layers at the beginning of thawing;however,as the frozen ground thaws continuously,the infiltration of the liquid water increases and the deep soil can store water like a sponge,accompanied by decreasing surface runoff.The influence of the soil freeze-thaw process on surface hydrologic and thermal fluxes varies seasonally and spatially.     

Radiation balance and the response of albedo to environmental factors above two alpine ecosystems in the eastern Tibetan Plateau

Understanding the energy balance on the Tibetan Plateau is important for better prediction of global climate change. To characterize the energy balance on the Plateau, we examined the radiation balance and the response of albedo to environmental factors above an alpine meadow and an alpine wetland surfaces in the eastern Tibetan Plateau, using 2014 data. Although our two sites belong to the same climatic background, and are close geographically, the annual incident solar radiation at the alpine meadow site(6,447 MJ/(m2·a)) was about 1.1 times that at the alpine wetland site(6,012 MJ/(m2·a)),due to differences in the cloudiness between our two sites. The alpine meadow and the alpine wetland emitted about 38%and 42%, respectively, of annual incident solar radiation back into atmosphere in the form of net longwave radiation; and they reflected about 22% and 18%, respectively, of the annual incident solar radiation back into atmosphere in the form of shortwave radiation. The annual net radiation was 2,648 and 2,544 MJ/(m2·a) for the alpine meadow site and the alpine wetland site, respectively, accounting for only about 40% of the annual incident solar radiation, significantly lower than the global mean. At 30-min scales, surface albedo exponentially decreases with the increase of the solar elevation angle; and it linearly decreases with the increase of soil-water content for our two sites. But those relationships are significantly influenced by cloudiness and are site-specific.     

Soil restoration research advances of artificial sand-binding vegetation ecosystem in the Tengger Desert,Northern China

Soil plays an important role in desert ecosystem, and is vital in constructing a steady desert ecosystem. The management and restoration of desertified land have been the focus of much discussion. The soil in Shapotou desert region has developed remarkably since artificial sand-binding vegetation established in 1946. The longer the period of dune stabilization, the greater the thickness of microbiotic crusts and subsoil. Meanwhile, proportion of silt and clay increased significantly, and soil bulk density declinced. The content of soil organic matter, N, P, and K similarly increased. Therefore, soil has developed from aeolian sand soil to Calcic-Orthic aridisols. This paper discusses the effects brought about by dust, microbiotic soil crust and soil microbes on soil-forming process. Then, we analyzed the relation between soil formation and sand-binding vegetation evolution, in order to provide a baseline for both research on desert ecosystem recovery and ecological environment governance in arid and semi-arid areas.     

基于遥感的黄河三角洲蒸散的动态分析

Evapotranspiration (ET) is an important parameter for water resource management. Compared to the traditional ET computation and measurement methods, the ET computation method based on remote sensing has the advantages of quickness, precision, raster mapping and regional scale. SEBAL, an ET computation model using remote sensing method is based on the surface energy balance equation which is a function of net radiance flux, soil heat flux, sensible heat flux and latent heat flux. The former three fluxes can be computed through the parameters retrieved from remote sensing image, then the latent heat flux can be obtained to provide energy for ET. Finally we can obtain the daily ET. In this study SEBAL was applied to compute ET in the Yellow River Delta of China where water resource faces a rigorous situation. Three Landsat TM images and meteorology data of 1999 were used for ET computation, and spatial and temporal change patterns of ET in the Yellow River Delta were analysed.     

And the Question Shall Determine the Method

Book Reviews are in this Articles.

Rural Communities under Stress: Peasant Farmers and the State in Africa Jonathan Barker. Cambridge: Cambridge University Press, 1989. ix and 228 pp., maps, diags., index, and biblio. $44.50 cloth (ISBN 0-521-30867-4); $13.95 paper (ISBN 0-521-31358-9).

Atop the Urban Hierarchy. Robert A. Beauregard, ED. Totowa, NJ: Rowman and Littlefield Publishers, Inc., 1989. xx and 304 pp., maps, diags., index, and biblio. $33.50 cloth (ISBN 0-8476-7554- 8).

Commonplaces. Essays on the Nature of Place. David W. Black, Donald Kunze, AND John Pickles, EDS. Lanham, MD: University Press of America, 1989. iv and 140 pp., biblio. $18.50 cloth (ISBN 0-8191-7387-8).

The Behavioural Environment: Essays in Reflection, Application, and Re-evaluation. Frederick W. Boal AND David N. Livingstone, EDS. London and New York: Routledge, 1989. xx and 337 pp., maps, diags., photos, index. $62.50 cloth uation. (ISBN 0-415-00454-3).

The Road to Botany Bay. Paul Carter. Chicago: The University of Chicago Press, 1989. xxv and 384 pp., maps, illus., notes, and index. $16.95 paper (ISBN 0-226-09516-9).

Research in Human Geography. John Eyles, ED. London and New York: Basil Blackwell, 1988. x and 210 pp., figs., tables, index, and biblio. $55.00 cloth (ISBN 0-631-15009-9).

Soil: Morphology, Genesis, and Classification. Delvin S. Faning AND Mary C.B. Faning. New York: Wiley, 1989, xx and 395 PP., diags. photos tables, maps, app., gloss., index, and biblio. $57.50 cloth (ISBN 0471-89248-3).

Development in Marginal Areas. Gerhard Gustafsson, ED. Karlstad, Sweden: University of Karlstad, 1989. ii and 168 pp., maps, diags., and biblio. N.p. paper (ISSN 0282-5309).

The Fate of the Forest: Developers, Destroyers and Defenders of the Amazon.Susanna Hecht AND Alexander Cockburn. London and New York: Verso, 1989. x and 266 pp., maps, apps., one diag., index, gloss., and biblio. $24.95 cloth (ISBN 0-86091-261-2).

Understanding Leisure and Recreation: Mapping the Past, Charting the Future. Edgar L. Jackson AND Thomas L. Burton, EDS. State College, PA: Venture Publishing, Inc. 1989. xiv and 653 pp. $31.95 cloth (ISBN 0-910251-34-7).

Maps of Meaning: An Introduction to Cultural Geography. Peter Jackson. London: Unwin and Hyman, 1989. xvii and 213 pp., maps, figs., photos, biblio, and index. $60.00 cloth (ISBN 0-04-445365-5) and $17.95 paper (ISBN 0-040445366-3).

Remaking Human Geography. Audrey Koboyashi AND Suzanne Mackensie, EDS. Boston: Unwin and Hyman, 1989. xii and 273 pp., map, illus., tables, index, and biblio. $55.00 cloth (ISBN 0-04- 445324-8); $21.95 paper (ISBN 0-04- 445325-6).

Adapting to Drought: Farmers, Famines and Desertification in West Africa. Michael Mortimore. Cambridge: Cambridge University Press, 1989. xxii and 299 pp., maps, diags., index, and biblio. $59.50 cloth (ISBN 0-521-32312-6).

Native American Architecture. Peter Nabokov AND Robert Easton. New York: Oxford University Press, 1989. 431 pp., maps, photos, sketches, gloss., index, refs. $36.00 cloth (ISBN 0-19-503781-2).

Explorations in the Understanding of Landscape: A Cultural Geography. William Norton. Contributions in Sociology, No. 77. New York: Greenwood Press, 1989. xii and 201 pp., illus., tables, biblio., index. $39.95 cloth (ISBN 0-313-26494-5).

The Cambridge Encyclopedia of India, Pakistan, Bangladesh, Sri Lanka, Nepal, Bhutan, and the Maldives. Francis Robinson, ED. Cambridge: Cambridge University Press, 1989. 520 pp., maps, diags., photos, gloss., biblio., index. $49.50 cloth (ISBN 0-521-33451-9).

The Contemporary Atlas of China. Nathan Sivin, ED. Boston: Houghton Mifflin Co., 1988. 200 pp, maps, diags., tables, and index. $39.95 (ISBN 0-395-47329-2).

Planned Development in the Socialist World. Graham Smith. Cambridge: Cambridge University Press, 1989. vi and 106 pp., maps, tables, figs., gloss., index, and biblio. $19.95 cloth (ISBN 0-521-30546-2).

The Evolution of Regional Economies: Entrepreneurship and Macroeconomic Change. Luis Suarez-Villa. New York: Praeger Publishers, 1989. xvii and 263 pp., tables, figs., apps., notes, biblio., and index. $45.00 cloth (ISBN 0-275-93 198-6).

Migrants in the Mexican North: Mobility, Economy, and Society in a Colonial World. Michael M. Swann. Boulder, CO: Westview Press, Dellplain Latin American Studies No. 24, 1989. xv and 202 pp., maps, tables, figs., biblio., app., and index. $28.50 (ISBN 0-8 133-7782-X).

Population and Resources in Western Intellectual Traditions. Michael S. Teitelbaum AND Jay M. Winter, EDS. Cambridge: Cambridge University Press, 1989. vii and 310 pp., $49.50 cloth (ISBN 0-521-37538-X).

Ground Subsidence. A. C. Waltham. Glasgow and London: Blackie and Son; New York: Chapman and Hall, 1989. ix and 202 pp., maps, diags., photos, refs., and index. $95.00 (ISBN 0-412-01801-2).     

Model of the geoelectrical structure of the mid- and lower mantle in the Europe–Asia region

The conductivity structure of the Earth's mantle was estimated using the induction method down to 2100  km depth for the Europe–Asia region. For this purpose, the responses obtained at seven geomagnetic observatories (IRT, KIV, MOS, NVS, HLP, WIT and NGK) were analysed, together with reliable published results for 11  yr variations. 1-D spherical modelling has shown that, beneath the mid-mantle conductive layer (600–800  km), the conductivity increases slowly from about 1  S  m⁻¹ at 1000  km depth to 10  S  m⁻¹ at 1900  km, while further down (1900–2100  km) this increase is faster. Published models of the lower mantle conductivity obtained using the secular, 30–60  yr variations were also considered, in order to estimate the conductivity at depths down to the core. The new regional model of the lower mantle conductivity does not contradict most modern geoelectrical sounding results. This model supports the idea that the mantle base, situated below 2100  km depth, has a very high conductivity.     

Macrozoobenthos in the inshore zone of the Northern Aral Sea

The macrozoobenthos was investigated at eight sites in the Aral Sea inshore zone and in the lower reaches of the Syrdaria river. In the sea, the benthos comprised bivalve molluscsSyndosmya segmentum Recluz andCerastoderma isthmicum Issel, gastropods fromCaspiohydrobia Starob., the polychaeteNereis diversicolor O.F. Müller and the crabRhithropanopeus harrisii tridentatus (Maitland). In the Syrdaria, MysidaeParamysis lacustris (Czern.) and GammaridaeDikerogammarus aralensis (Uljanin) were found. These taxa have not been recorded from the Sea since the 1970s. The total zoobenthos biomass and density varied between the investigated Sea areas from 92 to 582 g/m² and from 1,600 to 39,000 ind./m², respectively. Spatial and temporal salinity changes within the range 20–41 g/L did not affect macrozoobenthos composition and structure. The conclusion is that the benthic ecosystem of the Aral Sea was in a state of comparative stability from the middle of the 1980s to the middle of the 1990s. Analysis of the zoobenthos in the inshore zone is proposed as a convenient and accessible method for monitoring the status of the zoobenthos of the entire Aral Sea.     

Chemical composition of waters and the phytoplankton of the lakes within the delta of the Selenga river

Field observations showed that the characteristics of chemical composition of waters and the development of plankton algae in the lakes within the delta of the Selenga river are determined by their flowage. The most open Lake Nekipelovskoe communicates with the Selenga outlets throughout a year, and Lake Zavernyaikha only at the period of an open channel. Lake Semenovskoe and Lake Khlystov Zaton are located in the islands and are isolated from the outlets. According to composition of main ions, the lakes under investigation refer to the hydrocarbonate class, the calcium group. The sum of ions in the water of Lake Nekipelovskoe approaches the one in the Selenga (86?221 mg/dm³), and the highest sums of ions were recorded in the wintertime in the lakes isolated from the outlets (446?743 mg/dm³). The lakes of the delta are characterized by a high trophicity. The maximum concentrations of total phosphorus in Lake Nekipelovskoe and Lake Zavernyaikha were 68 and 122 μg mg/dm³, and in Lake Semenovskoe and Lake Khlystov Zaton ?0.8 and ?0.63 μg mg/dm³, respectively. The most intense development of algae is observed in Lake Zavernyaikha, which is due to the high population of Baikal endemics. Lake Zavernyaikha showed a close negative correlation between the concentration of NO ₃ ^? , mineral phosphorus and phytoplankton biomass; the correlation coefficient was ?0.8 and ?0.63, respectively. The lakes exhibited increased contents readily hydrolysable organic matter, and a decrease in dissolved oxygen concentration in winter; hydrogen sulfide was repeatedly recorded in Lake Khlystov Zaton. The water quality in the lakes during the springtime varies from “quite clean” to “weakly polluted”; at low-water periods, especially in winters, it can drop to the category of “exceedingly dirty”. The water quality of the Selenga can be influenced by the lakes during spring floods when material accumulated during the wintertime is transported to the river outlets and further to Lake Baikal.     

珠江广州河段微表层与次表层水环境质量比较(英文)

The water quality in the surface microlayer(SML) and subsurface water(SSW) in the Guangzhou segment of Pearl River, a eutrophic urban river section in China, were analyzed. The spatial and temporal dynamics of nutrient concentrations, heavy metals and bacteria were examined from two sampling sites in monthly samples throughout 2010. The mean concentrations of total nitrogen, ammonia, nitrate and nitrite were higher than 7.0 mg/L, 3.1 mg/L, 1.1 mg/L and 0.3 mg/L, while total phosphorus and orthophosphate were 0.5 mg/L and 0.1 mg/L, respectively. These results indicated that the water quality was rich in minerals and eutrophic. The mean concentrations of Mn and Fe were higher than 0.013 mg/L; and Ni, Cr and Pb were higher than 0.001 mg/L. The mean concentrations were in the order of Mn Fe Ni Pb Cr. The concentrations of heavy metals in the Guangzhou segment were lower than the limit of the surface water quality standards in China and the World Health Organization(WHO), but higher than the median values in the world's freshwater. The density of bacteria ranged from 3.30×105 to 5.23×106 cells/mL, and the amount of cultivable heterotrophic bacteria ranged from 1.30×10 3 to 1.89×10 6 cfu/mL. Fecal coliform levels were beyond the V class of China water quality standard. The SML was enriched in nutrients, heavy metals and bacteria, with the maximum enrichment factor of 3.84 for nutrients, 8.00 for heavy metals, and 3.04 for bacteria, suggesting that the water quality of the SML of the Guangzhou segment of the Pearl River was more serious than in the SSW.     

长江口滨岸湿地沉积物对上覆水体中无机氮的净化能力估算

Estuarine wetlands serve as a natural barrier to remove the land-generated pollut-ants and attenuate the pollutant load from the land to the sea. As one of the most important estuarine wetlands, the Yangtze estuarine wetlands have attracted particular interests in the biogeochemical studies of nutrients. The objectives of this study were to characterize the seasonal and spatial distribution of dissolved inorganic nitrogen (DIN) fluxes across the sediment-water interface; to calculate the total DIN fluxes in a year and different seasons; and to evaluate the DIN removing capability of the sediment in the tidal wetlands of the Yangtze Estuary. The spatial distribution of DIN fluxes shows complicated seasonal variations and spatial differences. The annual DIN fluxes range from -22.22 mmol N m-2 h-1 to 19.54 mmolN m-2 h-1, with an average of -1.48±1.34 mmol N m-2 h-1. The tidal wetlands in the Yangtze Estuary behave as a source of water DIN in spring when DIN is released from sediment into overlying water, and the released amount of DIN is 1.33×104 tons of nitrogen (T N). In sum-mer, autumn and winter, the sediment absorbs the DIN from the overlying water, and the absorbed amounts of DIN are 4.36×104 T N, 6.81×104 T N and 2.24×104 T N, respectively. The average amount of DIN in overlying water of the Yangtze Estuary is 52.6×104 T N yr-1, and the perennial average amount of DIN absorbed from the overlying water by the sediment is 12.1×104 T N yr-1. The annual DIN elimination rate of the tidal wetlands was 23.0%.     

Modeling the morphology of gully cross sections in the Yuanmou Dry-hot Valley

Abstract

Characterizing gully cross sections (GCs) is essential for calculating the volume and erosion rate of the gully. However, little research has focused on modeling the morphology of GCs. This study investigated 456 GCs with a laser distance meter located at the mouth, middle, and head of 152 gullies in the Yuanmou Dry-hot Valley of China; mapped them with AutoCAD software; fitted them with 2nd–6th degree polynomial functions, and discussed the correlation between the coefficients and the morphology of GCs. The results showed that: (1) using a 2nd-degree polynomial function (y = ax² + bx + c) to describe the morphology of GCs produced a better result than other polynomial functions; (2) the coefficient a of 2nd-degree polynomial function was correlated with depth (r = ?0.226, p < 0.01), gradient (r = 0.545, p < 0.01), and activities; and (3) the symmetry axis (?b/2a) of 2nd-degree polynomial function increased with gully change from left-deflection to right-skewed, and the absolute value showed the asymmetrical degree (r = 0.216, p < 0.01). This study will not only help to understand the morphology and evolution of gullies, but will also provide a scientific basis for prevention of gully erosion.     

青藏高原不同时段气候变化的研究综述

1 Introduction The annual mean world temperature increased by about 0.6℃ from the late 1800s to the 1980s (Wang, 1994). The global environmental change is marked with “global warming” and its possible effects on the ecosystem as well as the production …     

On the Relation between the Meteorological Conditions and the Freezing of Lusterfjord

Abstract|Gjessing,

Y. T. 1968. On the Relation between the Meteorological Conditions and the Freezing of Lusterfjord. Norsk geogr. Tidsskr. 22, 200–208,

In most cases Lusterfjord freezes over in winter immediately after a period of mild weather conditions with some precipitation. It is sufficient to have temperatures just below 0°C for a relatively short period of time in order for ice to form. However, during extreme cold weather conditions where the temperatures are under -15°C for a lengthy period of time, the fjord is often free from ice formation.

In order for ice to form, there must be a stable gradient in the uppermost centimetres of the water masses. This stable cross-section is a result of a strong gradient of salinity and is formed by a supply of fresh water in the form of precipitation. Such a layer will easily be decomposed by a mechanical turbulence (wind).